One scheme for communication between user-thread library and the kernel is…
2013
One scheme for communication between user-thread library and the kernel is known as
Answer: C. Scheduler activation — ConceptA user-level thread library manages threads in user space, while the kernel schedules the execution resources. A coordination interface between these…
- A.
Lightweight process
- B.
Upcall handler
- C.
Scheduler activation
- D.
Cleanup handler
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Correct answer: C
Concept
A user-level thread library manages threads in user space, while the kernel schedules the execution resources. A coordination interface between these layers must convey available processors and events such as blocking or preemption.
Application
Under scheduler activations, the kernel assigns virtual processors to the process so that the user-level scheduler has execution contexts on which to run user threads.
When a user thread blocks, is preempted, or becomes runnable, the kernel sends an upcall; the user-level scheduler then remaps its user threads as needed.
Therefore, the overall communication and coordination scheme is called scheduler activation.
Contrast and cross-check
A lightweight process is a kernel-schedulable execution context, not the name of the complete coordination interface.
An upcall handler processes a kernel notification; it is one component used by the scheme.
A cleanup handler runs cleanup actions when a thread exits or is cancelled.
Thus, the required scheme is scheduler activation.